Why do some animals build structures and others don't? And how do animals decide where to build? Animal homes need to be safe and secure, protection from predators and the weather. Going above ground and under, viewers will investigate just what goes into making a home for a wild animal when cost is not a factor.

Harpy eagles are the most powerful birds of prey in the world. Standing three feet tall, with a six-foot wingspan and razor-sharp talons the size of bear claws, these birds are the heavyweight hunters of the South American rainforest. But scientists know very little about harpy eagles because their numbers are few, their habitat is large, they never soar above the trees, and they rarely come to the ground. Nature enters their secret world with wildlife...

Follow the epic journey of wildlife conservationist and bear biologist Chris Morgan as he travels by motorcycle across Alaska while filming the PBS Nature documentary Bears of the Last Frontier. From thick forests to the icy arctic, his immersion into the bears' world reveals, as never witnessed before, an astonishingly intimate portrait of North America's three bear species: brown bears, black bears, and polar bears.